Despite the advantages of listening with two ears, localization and spatial segregation of speech and noise remain difficult for patients who use two cochlear implants (CIs) or a CI in combination with a hearing aid (HA). The long-term goal of this research is to develop training methods that improve CI patients' binaural perception. For bilateral CI and bimodal patients, is it better to train with one ear or two? The answer may depend on the peripheral input to each ear, the specific deficit, and the listening task. The proposed study aims to evaluate the relative effectiveness of different monaural and binaural training approaches in bilateral CI and bimodal patients. We hypothesize that monaural training is better when listeners must adapt to a poor unilateral pattern from the CI; the most effective approach may depend on the nature of the unilateral deficit. Conversely, we hypothesize that binaural training is better when listeners must learn to combine redundant (similar CI+CI) or complementary (CI+HA) information; binaural training most likely targets somewhat different adaptation processes for bilateral CI and bimodal patients. Finally, we hypothesize that spatial training must target the very different listening demands of localization and spatial segregation of speech and noise; bilateral CI and bimodal patients most likely differ in their attention to low frequency cues for localization and segregation. The two Specific Aims - improving bilateral (Aim 1) and bimodal (Aim 2) binaural perception via auditory training - are highly innovative, in that the research seeks to identify the best training approach for different patient groups, as wel as understand how differences in the peripheral input may influence training outcomes. The conceptual framework is also innovative, in that the different training methods target different factors that may limit bilateral CI and/or bimodal performance: spectro-temporal resolution, tonotopic mismatch, and/or spatial perception. While the proposed experiments will evaluate different aspects of auditory training somewhat independently, there are areas of overlapping consideration that may be combined to advance auditory rehabilitation techniques for CI patients. These proposed experiments have great theoretical significance, as the results will shed light on auditory plasticity in electric hearing and in combined electric and acoustic hearing. The experiments have even greater clinical significance, as the results will provide strong evidence of the benefits of auditory training, hopefully leading to affordable, efficient an effective rehabilitation that CI patients can perform at home, using personal computers. We expect that these training approaches will generalize to improved performance outside the lab. As recent advances in implant technology seem to be reaching the point of diminishing returns, auditory training may provide the most cost-effective approach for CI patients to maximize the benefit of the implant device.